title: Enhanced contractility and myosin phosphorylation induced by Ca(2+)-independent MLCK activity in hypertensive rats.
abstract: OBJECTIVE
  The role of Ca(2+) sensitization induced by a Ca(2+)-independent myosin light chain kinase (MLCK) in hypertension has not been determined. The aim of this study was to clarify the role of possible Ca(2+)-independent MLCK activity in hypertension.
  
  
  RESULTS
  We compared increases in contractile force and phosphorylation of myosin light chain (MLC) evoked by calyculin A, a phosphatase inhibitor, in β-escin-permeabilized mesenteric arteries at pCa 9.0 between spontaneously hypertensive rat (SHR) and Wistar Kyoto rat (WKY). We found that there was no detectable phosphorylation of MLC at pCa 9.0, but that the administration of 1 μM calyculin A gradually increased force and mono- and di-phosphorylation of MLC. This contraction was inhibited by staurosporine but not by wortmannin, Y-27632, or calphostin-C. The calyculin A-induced contraction was significantly greater in the SHR than in the WKY and was associated with an increase in mono- and di-phosphorylation of MLC. SM-1, a zipper-interacting protein kinase (ZIPK)-inhibiting peptide, significantly inhibited the amplitude of the calyculin A-induced contraction and di-phosphorylation. Total ZIPK expression (54 + 32 kDa) was greater in the SHR than in the WKY. Phosphorylation of myosin phosphatase target subunit at Thr(697), but not at Thr(855), was consistently stronger in the SHR than in the WKY in calyculin A-treated tissues at pCa 9.0.
  
  
  CONCLUSIONS
  Our results suggest that Ca(2+)-independent MLCK activity is enhanced in the SHR, and that ZIPK plays, at least in part, an important role as a candidate for this kinase in rat mesenteric arteries.
authors.affiliation: Department of Physiology, College of Medicine, BK 21 Project for Medical Sciences, Yonsei University, CPO Box 8044, Seoul 120-752, Korea.
authors.forename: Young-Eun
authors.initials: YE
authors.lastname: Cho
authors.forename: Duck-Sun
authors.initials: DS
authors.lastname: Ahn
authors.forename: Kathleen G
authors.initials: KG
authors.lastname: Morgan
authors.forename: Young-Ho
authors.initials: YH
authors.lastname: Lee
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D064550:Death-Associated Protein Kinases; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006973:Hypertension / Q000201:enzymology* / Q000503:physiopathology; D008297:Male; D008387:Marine Toxins; D008638:Mesenteric Arteries / Q000201:enzymology / Q000503:physiopathology; D009124:Muscle Proteins / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000201:enzymology* / Q000503:physiopathology; D018994:Myosin Light Chains / Q000378:metabolism*; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010080:Oxazoles / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D054645:Protein Phosphatase 1 / Q000378:metabolism; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D015854:Up-Regulation; D014661:Vasoconstriction / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000494:pharmacology
chemical_list: D051017:Apoptosis Regulatory Proteins; D004791:Enzyme Inhibitors; D008387:Marine Toxins; D009124:Muscle Proteins; D018994:Myosin Light Chains; D010080:Oxazoles; D010750:Phosphoproteins; C491519:Ppp1r14a protein, rat; D014662:Vasoconstrictor Agents; C059041:calyculin A; D064550:Death-Associated Protein Kinases; D011493:Protein Kinase C; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D009219:Myosin-Light-Chain Kinase; D010749:Phosphoprotein Phosphatases; C499850:Ppp1r12a protein, rat; D054645:Protein Phosphatase 1